Can' figure this one out.........perhaps a smarter person than I can....
Have just built a R90 STD for an MD-500 fuse, and went for setup and tuning flights today before installing the mechs in the fuse.
Anyway, turned the main needle out 3 turns from stop and left idle mixture screw untouched. Fired her up and just revved like crazy (i.e. holding the head while the clutch burns crazy). Cutoff fuel to stop it.
Checked servo directions, throttle curve, etc. Seemed like all the throttle range was compressed into the first 15 degrees of throttle movement. Thought this might the result of a way-too-lean idle so brought the idle mix out a lot and problem is reduced.
BUT, it still seems as if the throttle range is 'compressed' - for example, my idle occurs at 5% on the throttle curve, but when I go to 8%, engine really revs and clutch engages. It looks like the engine is maxed out at only about half of the throttle range.
I've got a TT60 on the Rappy 50 and an OS-91 C-spec in my 90SE and never seen this before. Using 20% nitro and synthetic oils.